The present invention relates to an air-cooled oil-free rotary-type compressor and, more particularly, to an air-cooled oil-free rotary-type compressor having a compact cooling system.
In, for instance, U.S. Pat. No. 4,725,210, an oilless rotary-type compressor system is proposed which includes, inter alia, an oilless rotary compressor, a precooler and an after cooler for compressed air, a check valve, a jacket, a coolant cooler, a coolant pump, a transmission mechanism, an oil pump, an oil cooler and a cooling fan. In this conventional compressor system, the precooler is a liquid-cooled cooler which cools compressed air delivered from the compressor by using a cooling liquid (hereafter referred to as a coolant). By using cooling air from a cooling fan, the coolant cools the compressor coolant which cools a compressor body by circulating through the jacket and the coolant circulating through the precooler.
A disadvantage of the above-described rotary-type compressor system resides in that compressed air delivered from the compressor is cooled by the precooler which is a liquid-cooled cooler, and the coolant which has been subjected to heat exchange by this precooler and the jacket of the compressor is cooled by the coolant cooler which is an air-cooled cooler. Therefore, the coolant warmed to 60.degree.-80.degree. C. or thereabout is supplied to the coolant cooler, and a temperature difference with the cooling wind of about 20.degree.-40.degree. C. which in a cooling medium is small, so that it has been necessary to use a large-capacity coolant cooler. A large coolant cooler results in increasing the price of the compressor and constitutes a factor hindering a reduction in the size of the compressor.